1. Technical Field
The present invention relates to a template washing method for photowashing a template used for nanoimprint, a pattern forming method using a template washed by the template washing method, a photowashing apparatus used for the template washing method, and a nanoimprint apparatus provided with the photowashing apparatus.
2. Description of the Related Art
In recent years, in manufacture of semiconductor chips and biochips, a nanoimprint technology draws attention as a method capable of achieving the manufacture at lower costs in comparison with a pattern forming method using photolithography and etching of the related art.
In the pattern forming method using the nanoimprint technology, processes of forming a nanoimprint material layer on a substrate on which a pattern is to be formed, for example, on a wafer by applying a nanoimprint material including liquid-state resist of a light-cured type or a thermoset type, bringing a template (mold) formed with a pattern which is a negative pattern of the pattern to be formed into contact with the nanoimprint material layer and, in this state, performing a curing process on the nanoimprint material layer, and then separating the template from the obtained cured resin layer are performed (see JP-A-2000-194142 and JP-A-2008-91782).
In such a pattern forming method, when a resist residual exists on a surface of the template, a pattern obtained may have a defect, so that the surface of the template needs to be washed.
Therefore, as a method of washing the template, a method of immersing a pattern surface of the template into a cleaning agent such as water, then irradiating the pattern surface of the template with ultraviolet light to generate radicals such as oxygen radical or OH radical by photoexciting the cleaning agent, and degrading and removing the resist residual by the radicals (see JP-A-2010-46923) is known.
Therefore, in such a washing method, there is a problem that when the pattern surface of the template is immersed in the cleaning agent, the resist residual is dispersed in the cleaning agent, and hence a secondary contamination occurs by adhesion of the resist residual dispersed in the cleaning agent again to the template during the following template washing.
Also, there is a problem that production efficiency is lowered because the washing of the template needs to work to remove the template from a nanoimprint apparatus, and then mount the template on the nanoimprint apparatus after the washing of the template is ended, and hence a pattern forming process must be stopped for a long time.
In contrast, in a process of manufacturing the liquid crystal display device or the like, a photowashing method is used as means for washing a glass substrate (see JP-A-8-236492).
In the photowashing method, a surface of the glass substrate is irradiated with vacuum ultraviolet light and hence foreign substances are degraded by energy of the vacuum ultraviolet light, and the degraded substances are oxidized and gasified by active oxygen such as radical oxygen, or ozone generated by irradiation of oxygen in the air with the vacuum ultraviolet light, and consequently, the foreign substances existing on the surface of the glass substrate are removed.
However, it was found that resist residual can hardly be removed reliably when the photowashing method used in the process of manufacturing the liquid crystal display device or the like is applied for washing the template.
After a great deal of diligent consideration on such problems, the inventor estimated that sulfuric acid, phosphoric acid, and other sulfur compound, or phosphorous compound were generated by the reaction of elemental sulfur or elemental phosphorus contained in the resist residual with water in the air, and the sulfur compound and the phosphorous compound stayed on the pattern surface of the template, and reached the invention on the basis of this knowledge.